Figure 5: Tcf7l2 coordinates with Sox10 to regulate OL terminal differentiation.

(a) De novo motif analysis identified Tcf7l2/Tcf4, Sox10-binding motifs as most significant binding motifs in Tcf7l2-binding regions in mOLs. (b) ChIP-seq binding profiles of Sox10 around Tcf7l2 peak summits in mOLs. (c) Heatmap of the signal intensities from ChIP-seq assays of Tcf7l2 and Sox10 across Tcf7l2-binding sites (±1 kb) called in mOLs. (d) Sox10 co-immunoprecipitated with Tcf7l2 in mOLs. (e) Visualization of Tcf7l2-binding profiles in OPCs, iOLs and mOLs on representative myelin gene loci (Mbp, Myrf, Olig1,Ugt8 and Zfp191). Sox10/Tcf7l2 co-occupancy (highlighted) in mOLs was also shown. (f) qRT–PCR assay for Mbp, Cnp expression in OPCs transfected with expression vectors for Tcf7l2, Sox10 or both; n=3 independent experiments. (g) The expression vector carrying Flag-Tcf7l2 was co-transfected with HA-Sox10 and a varied amount of Myc-Kaiso in 293T cells for 48 h. Lysates were co-immunoprecipitated with anti-Flag-Tcf7l2 and subjected to western blot analysis. Glyceraldehy 3-phosphate dehydrogense (GAPDH) as a loading control. (h) Model of Tcf7l2 regulation of OL differentiation through sequential interactions with Kaiso and Sox10 to promote stepwise OL lineage differentiation. At the onset of OPC differentiation, Tcf7l2 binds Kaiso to inhibit Wnt signalling activation and subsequently associates with Sox10 to promote OL maturation. Data are presented as mean±s.e.m. *P<0.05, **P<0.01 and ***P<0.001; analysis of variance (ANOVA) with Newman–Keuls multiple comparison test.